1. Technical Field
The present invention relates to an optical information reproducing apparatus and an optical information reproducing method using the same, and more particularly, to an optical information reproducing apparatus which can control a tracking position using optical information of a peripheral beam adjacent to a reproduction beam to be reproduced at the time of reproducing optical information, and an optical information reproducing method.
2. Background Art
Generally, as an optical data recording device for storing optical information, a compact disc (CD), a digital versatile disc (DVD), a high-definition DVD (HD-DVD), and a blu-ray disc (BD) are known.
With recent rapid development of information and computer industries, there is a need for a next-generation storage system which can satisfy a large storage capacity and high-speed data input and output ability.
One of systems having attracted an attention to satisfy the need is an optical information processing system using a principle of volume holography, that is, a holographic optical information processing system.
The holographic optical information processing system is contrived in consideration of a principle that two beams having different incident angles are intersected at a predetermined position on a photosensitive medium sensitive to beam to record an interference pattern, which is formed by means of interference of two beams, in the photosensitive medium.
That is, an interference pattern, which is formed by allowing a signal beam including data information and a reference beam irradiated at an angle different from that of the signal beam to intersect each other at a predetermined position on an optical information recording medium which is a photosensitive medium, is recorded on the optical information recording medium. At the time of reproducing optical information, the original data are restored using a diffracted image generated from the interference pattern by irradiating only a reference beam to the recorded interference pattern.
The holographic optical information processing system can repeatedly record data at the same position of an optical information recording medium in a three-dimensional manner by the use of a variety of multiplexing methods. By employing such a repeated recording process, it is possible to markedly enhance the storage capacity of an optical information recording medium having a limited area, thereby embodying a super large capacity storage system.
Examples of the multiplexing methods can include an angle multiplexing method, a phase-code multiplexing method, a wavelength multiplexing method, a fractal multiplexing method, a shift multiplexing method, a peristrophic multiplexing method, and a polytopic multiplexing method.
The holographic optical information processing system has been studied so as to enhance a data recording density by appropriately using the multiplexing methods. For example, the holographic optical information processing system operates such that the density of a signal beam is enhanced at the time of recording data and a reproduction beam to be reproduced is transmitted and the other peripheral beam is blocked by a beam splitter having a through hole formed therein.
However, such a holographic optical information processing system is sensitive to an environment variation such as a shaking of an apparatus, because the reproduction beam is allowed to pass through the through hole of the beam splitter.
Therefore, an accurate tracking servo control process is required. That is, there is required a process of checking whether a reproduction beam is accurately detected from a desired track and correctly positioning the track through a servo control process when the track is not correctly positioned.
When the tracking servo control process is not properly performed, the reproduction beam to be reproduced does not pass through a slot and a beam detector cannot acquire a correct image of optical information, thereby causing an increase in error rate. Accordingly, there is a great need for a technology of accurately and efficiently performing a tracking control process at the time of reproducing holographic optical information.